[GIT PULL] Followup single fix for block IO core pull

[GIT PULL] Followup single fix for block IO core pull

[Jens Axboe]

Hi Linus,

A commit in the previous pull request introduce a regression. So far
only observed on qemu-sparc64, but it's a general bug. Please pull this
single fix to rectify that, thanks.

  git://git.kernel.dk/linux-block.git for-linus

----------------------------------------------------------------
Jens Axboe (1):
      blk-mq: fix iteration of busy bitmap

 block/blk-mq.c         | 6 +++---
 include/linux/blk-mq.h | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

-- 
Jens Axboe

Re: [GIT PULL] Followup single fix for block IO core pull

[Dave Jones]

On Fri, Apr 17, 2015 at 09:12:01AM -0600, Jens Axboe wrote:
 > Hi Linus,
 > 
 > A commit in the previous pull request introduce a regression. So far
 > only observed on qemu-sparc64, but it's a general bug. Please pull this
 > single fix to rectify that, thanks.

I hit the same bug on two x86 boxes, bare-metal.
Reverting the commit Guenter pointed out made them boot again,
so definitely not sparc/qemu specific in any way.

I suspect the only reason more people didn't see it is that not
everyone is running with the mq-by-default config option yet ?

	Dave

Re: [GIT PULL] Followup single fix for block IO core pull

[Jens Axboe]

On 04/17/2015 09:41 AM, Dave Jones wrote:
> On Fri, Apr 17, 2015 at 09:12:01AM -0600, Jens Axboe wrote:
>   > Hi Linus,
>   >
>   > A commit in the previous pull request introduce a regression. So far
>   > only observed on qemu-sparc64, but it's a general bug. Please pull this
>   > single fix to rectify that, thanks.
>
> I hit the same bug on two x86 boxes, bare-metal.
> Reverting the commit Guenter pointed out made them boot again,
> so definitely not sparc/qemu specific in any way.
>
> I suspect the only reason more people didn't see it is that not
> everyone is running with the mq-by-default config option yet ?

It is puzzling. I ran it on several boxes, both multi queue and not, and 
both single mq queues and multiple. But the code is clearly wrong. So 
yeah, it's not sparc64 specific in any way. My initial thought was that 
this was another issue related to sparse CPU ids, but that's not the 
case. It's a plain bug, unfortunately.

-- 
Jens Axboe

Re: [GIT PULL] Followup single fix for block IO core pull

[Jens Axboe]

On 04/17/2015 09:45 AM, Jens Axboe wrote:
> On 04/17/2015 09:41 AM, Dave Jones wrote:
>> On Fri, Apr 17, 2015 at 09:12:01AM -0600, Jens Axboe wrote:
>>   > Hi Linus,
>>   >
>>   > A commit in the previous pull request introduce a regression. So far
>>   > only observed on qemu-sparc64, but it's a general bug. Please pull
>> this
>>   > single fix to rectify that, thanks.
>>
>> I hit the same bug on two x86 boxes, bare-metal.
>> Reverting the commit Guenter pointed out made them boot again,
>> so definitely not sparc/qemu specific in any way.
>>
>> I suspect the only reason more people didn't see it is that not
>> everyone is running with the mq-by-default config option yet ?
>
> It is puzzling. I ran it on several boxes, both multi queue and not, and
> both single mq queues and multiple. But the code is clearly wrong. So
> yeah, it's not sparc64 specific in any way. My initial thought was that
> this was another issue related to sparse CPU ids, but that's not the
> case. It's a plain bug, unfortunately.

It's the pre morning coffee issue, looks like. All my test boxes end up 
having >= map->bits_per_word CPUs, so the test cases never ran into the 
round down issue.

-- 
Jens Axboe